graph of V and R

Question

A cell of emf E having an internal resistance r is connected to an external resistance R . The potential difference V across the resistance R varies with R as shown in figure by which curve 

 http://i.imgur.com/N16ZP1s.jpg

Answer 1

The terminal voltage of a battery (V_term) is related to its EMF (ideal voltage) by:

 

V_term = E - ir

 

where 

 

r = the battery's internal resistance 

i = current through the battery and the rest of the circuit

 

Ignoring Joule heating effects and assuming r is constant, the key questions are:

 

-- As the external resistance R increases, what happens to i?

-- Given what happens to i, what then happens to V_term?

 

Since V_term is the voltage dropped across R, it is what the question is asking about.

 

Putting all these together points to one of the curves on the plot you attached.  If you would like to talk about it more, I am available for online sessions.